Self-regulating reciprocating piston pumps



July 21, 1964 P. E. BESSIERE 3,141,414-

SELF-REGULATING RECIPROCATING PIsToN Pumps Filed July l1, 1962 t' /NVENTOR ATTORNEYS r.' E M United States Patent O 3,141,414 SELF-REGULATING RECHPROCATBNG PISTN PUMPS Pierre Etienne Bessiere, Neuilly-sur-Seine, France, as-

signor to Societe Anonyme pour lExploitation des Procedes Chimiques et Physiques, Zug, Switzerland, a

Swiss company Filed .luly 11, 1962, Ser. No. 269,073 Claims priority, appli-cation France luly 2S, 1961 1 Claim. (Cl. 10S-41) The present invention relates to self regulating reciprocating piston pumps that is to say to pumps wherein the main active member (hereinafter called piston, this term being meant to include equivalent means, such as a diaphragm or a pair of opposed pistons working in a common cylinder) has a reciprocating movement, and the delivery of which on every piston stroke is adapted, at least within some ranges of operation, to decrease when the speed of the pump (number of strokes per unit of time) increases. My invention is more especially concerned with fuel injection pumps for internal combustion engines (this term including explosion engines and gradual combustion engines such as Diesel engines).

My invention relates to pumps comprising an auxiliary pump working in synchronism with the main pump, the delivery of said auxiliary pump being in communication, on the one hand, with a variable Volume space limited by a reciprocating member, hereinafter called shuttle or shuttle piston, which controls a by-pass conduit leading off from the main pump working chamber and, on the other hand, with the interposition of a check valve or the like, with an accumulator of liquid under pressure, the inside of this accumulator communicating permanently, through a throttled passage (preferably of adjustable cross-section area) with a low pressure space (such as the liquid tank from which the auxiliary pump is fed).

According to my invention, the total volume variation of the auxiliary pump working chamber, that of the variable volume space limited by the shuttle, the characteristic of the shuttle return spring, the law of variation of pressure in the accumulator as a function of the amount of liquid present therein and the cross-section area of said throttled passage are determined so that, for speeds of reciprocation of the main piston exceeding a given value, the shuttle is moved sufficiently far against the resistance of its return spring to open the by-pass conduit branching off from the main pump working chamber.

A preferred embodiment of my invention will be hereinafter described with reference to the appended drawings, given merely by way of example, and in which:

The only figure shows, indiagrammatic section, a fuel injection pump made according to the invention.

The pump comprises a main piston 1, driven by the engine to be fed with fuel by the pump through a rotating cam 2 and against the action of a return spring 3, this piston 1 moving in a sliding manner in a main cylinder 4. This cylinder is adapted to communicate with a feed conduit when piston 1 is in its lower dead center position. Furthermore cylinder 4 communicates with a delivery conduit 6, with the interposition of a check valve 7. Feed conduit 5 is branched on a fuel tank or on a transfer pump and conduit 6 leads to the injector or injectors of the internal combustion engine.

The pump self-regulating means comprise the following elements. A by-pass conduit 3 leads olf from the workingfchamber of cylinder 4 toward a fuel tank. This by-pass conduit 8 is controlled by a shuttle piston 9 provided with a groove 9a capable, for one position thereof, of opening by-pass conduit 8, this position being occupied by the shuttle when the extension 9b thereof cornes into contact with the top end of the cylinder 11 in which the shuttle is moving. The movement of the shuttle 9 in 3,141,414 Patented July 21, 1964 ICC the upward direction (i.e. in the direction which brings it into the above mentioned position where it opens bypass conduit 8) is produced by a hydraulic system, whereas the displacement of said shuttle in the opposed direction is produced by a spring 10, preferably adjustable, so that the shuttle at the end of its downward stroke is applied against an abutment 12 which determines its position of rest.

The above mentioned hydraulic system comprises an auxiliary pump, the piston of which moves in synchronism with the piston 1 of the main pump. Preferably as shown, the piston 13 of the auxiliary pump consists of a portion of enlarged diameter of the main piston 1, reciprocating in a cylinder 14 in line with the main cylinder 4 but of larger diameter. In the wall of cylinder 14, there is provided a feed conduit 15 which is opened when piston 13 is in its lower dead center position (as illustrated by the drawing), i.e. at the same time as the main piston 1 opens feed conduit 5.

A conduit 16 starts from the top end of cylinder 14 so as to connect the inside thereof constantly with the lower end of cylinder 11 in which shuttle 9 is slidable. Furthermore cylinder 14 is connected through a conduit 17 (which in the example shown starts from the lower end of cylinder 11 but which might be directly connected with conduit 16) with an accumulator 18 of liquid under pressure, with the interposition of a check valve 19 which opens when the pressure in conduit 17 is higher than that existing in accumulator 18 and which is otherwise closed. Accumulator 18 comprises a piston 18a pushed by a spring 2t) which is preferably adjustable. Thus the greater the amount of liquid contained in accumulator 18, the more piston 18a is moved toward the right and cornpresses spring 20, and the higher is the pressure in accumulator 18.

Return spring 10, which urges shuttle 9 in the downward direction, is the more compressed and consequently exerts a higher pressure on the shuttle as this shuttle is moved a greater distance in the upward direction from abutment 12.

Furthermore accumulator 1S is provided with a bypass conduit 21 comprising a throttled passage 22. Advantageously, as shown, this throttled passage 22 is adjustable for instance by means of a screw 23 as shown. The adjustment of the throttled passage may be performed either by the person in charge of the internal combustion engine, or by an automatic governor.

In order to obtain the opening of by-pass conduit 8 by shuttle 9 when the number of reciprocation of the pump pistons 1 and 13 per unit of time and therefore the speed of the internal combustion engine reach predetermined values, it is necessary to adjust the following elements:

(l) The total volume variation of the auxiliary pump working chamber on every stroke of the corresponding piston;

(2) The total volume variation of the space limited, at the bottom of cylinder 11, by shuttle 9 when it moves from its position of rest (in contact with abutment 12) to the position where it opens bypass conduit 8;

(3) The characteristic of spring 9;

(4) The law of the variation of the pressure in accumulator 18 as a function of the amount of liquid stored up in this accumulator. This law depends of course upon the volume variation conditions of the accumulator and upon the characteristic of spring 20; and

(5) The cross-section area of throttled passage 22, provided in by-pass conduit 21.

According to my invention all these values are adjusted in such manner as to obtain the following operation of the self regulating means.

When, during the delivery stroke of the fuel injection pump, auxiliary piston 13 forces liquid through conduit 16 into the bottom end of cylinder 11 and into conduit 17, for low speeds of reciprocation of pistons 1 and 13, the pressure of this liquid is relatively low and practically equal to the pressure in accumulator 1S. This results from the fact that, at low speeds, the amount of fuel introduced into accumulator 18 past check valve 19 during every delivery stroke of piston 13, is practicdly equal to the amount of fuel which can escape from accumulator 18 through by-pass conduit 21 during every time interval between two consecutive delivery strokes. This relatively low liquid pressure is not sufiicient to move shuttle 9 against the resistance of spring 10 (which resistance increases as the shuttleV is moving more and more upwardly) into the position where the groove 9a of the shuttle opens by-pass conduit 9. This by-pass conduit therefore remains closed in these conditions.

It is to be noted here that, during every time interval between two successive delivery strokes, shuttle 9 always comes back to its position of rest, determined by abutment 12. Furthermore, the pressure in accumulator 18 drops during each of these time intervals, due to the fact that liquid escapes to the outside through throttled passage 22 whereas, during every delivery stroke the pressure rises in the accumulator. Furthermore, during every period for which piston 13 clears the opening of feed conduit 1S, the feed of liquid into cylinder 14 is suffcient to fill up cylinder 14, conduits 16 and 17 and the variable volume space in cylinder 11 under the shuttle before piston 13 starts back upon a new delivery stroke.

When the number of reciprocations per unit of time of pistons 1 and 13 increases, the minimum and maximum pressures in accumulator 18 also increase but, as long as the pressures in said accumulator 1S remain lower than the liquid pressure required to push the shuttle 9 upwardly against the action of spring 1li to bring said shuttle into the position where it opens by-pass conduit 8, this conduit remains closed. It is only when the speed of pistons 1 and 13 reaches a ygiven value, for which at least the final pressures in accumulator 18 become equal to, or even higher than, the pressure necessary to move shuttle 9 upwardly into its opening position, that conduit 8 is opened by the shuttle before the end of the delivery stroke of piston 1, whereby the amount of fuel delivered by this piston, on every stroke thereof, into conduit 6 decreases. The shuttle, when it reaches its opening position, is stopped by the fact that its abutment 9b is applied against the upper end of cylinder 11.

If the speed further increases, the opening of by-pass conduit S takes place more and more early during the delivery stroke of piston 1 and consequently the amount of the fuel injected during this stroke decreases more and more. This is due to the fact that the minimum and maximum pressures in accumulator 18 increase when the speed increases and that, consequently, the pressure necessary to bring the shuttle into its opening position is reached more and more early during every delivery stroke as the speed of pistons 1 and 13 increases. Once the shuttle has been brought into its position where it opens by-pass conduit 8, the remainder of the liquid that is being driven by piston 13 passes into accumulator 18.

In order to vary the speed for which shuttle 9 begins 'to open by-pass conduit 8, Ifmay vary either the crosssection area of throttled passage 22 or the initial compression of spring 10 or the initial compression of spring or several of these factors simultaneously.

The regulation eliect obtained according to my invention therefore depends upon the ratio of the pressure existing in accumulator 13 to the pressure necessary to move the shuttle into its opening position. As long as the pressure in accumulator 18 is lower than that necessary to produce this displacement of the shuttle, the whole of the liquid delivered by piston 13, or at least a great portion of this liquid, enters into accumulator 18, from which a portion of this liquid escapes through bypass conduit 21 during the time intervals between two delivery strokes, when the shuttle comes back into its position of rest.

In a general manner While I have, in the above description, disclosed what I deem to be a practical and eiiicient embodiment of my invention, I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of my invention as comprehended Within the scope of the appended claim.

Vhat I claim is:

A self-regulating reciprocating piston pump which comprises, in combination, a main cylinder, a main piston slidable with a reciprocating movement in said main cylinder to define therewith a main variable volume working chamber, a liquid inlet conduit positioned to communicate with said main working chamber when the volume thereof is maximum, a delivery conduit leading oli from said working chamber, a by-pass conduit leading off from said working chamber, means forming a cylindrical recess fixed with respect to said main cylinder, a shuttle piston in said cylindrical recess and slidable between two end positions, said end positions being a first position and a second position, said shuttle being operable, in said second position thereof, to fully open said by-pass conduit, said shuttle piston defining with said cylindrical recess a variable volume space so that increase of the volume of said space corresponds to a movement of said shuttle piston in the direction from said first position toward said second position, a spring operatively connected with said shuttle piston for constantly urging it toward said first position thereof, an auxiliary pump cylinder fixed with respect to said main cylinder, an auxiliary pump piston slidable in said auxiliary cylinder to define therewith an auxiliary variable volume working chamber, said auxiliary piston being arranged to reciprocate in said auxiliary cylinder in synchronism with the movement of said main piston in said main cylinder, a liquid inlet conduit positioned to communicate with said auxiliary working chamber when the volume thereof is maximum, a conduit extending between said auxiliary working chamber and said variable volume space for permanently connecting said auxiliary Working chamber and said space with each other, an accumulator of liquid under pressure, mens for connecting said auxiliary chamber with said accumulator, said last mentioned means comprising a check valve opening only in the direction from said auxiliary chamber toward said accumulator, a permanently open by-pass conduit leading from said accumulator to the outside thereof, and means forming Va throttled passage in said last mentioned by-pass conduit, the total volume variation of said auxiliary working chamber, the volume variation of said variable volume space when said shuttle piston passes from its first position to its second position, the characteristic of said spring, the law of variation of the pressure in said accumulator as a function of the amount of liquid present therein, and the cross-section area of said throttled passage being determined so that, for speeds of reciprocation of said main piston above a given value, said shuttle piston is moved suiiiciently far against the resistance of said spring to open said rst mentioned bypass conduit.

References cited in the are of this parent FOREIGN PATENTS Y1,229,752 France Mar. 28, 1960 

